Global Cooling-Wanna Bet?

Global cooling appears to be the “flavour of the month”. First, a rather misguided media discussion erupted on whether global warming had stopped, based on the observed temperatures of the past 8 years or so (see our post). Now, an entirely new discussion is capturing the imagination, based on a group of scientists from Germany predicting a pause in global warming last week in the journal Nature (Keenlyside et al. 2008).

Specifically, they make two forecasts for global temperature, as discussed in the last paragraphs of their paper and shown in their Figure 4 (see below). The first forecast concerns the time interval 2000-2010, while the second concerns the interval 2005-2015 (*). For these two 10-year averages, the authors make the following prediction:

Their graph shows this: temperatures in the two forecast intervals (green points shown at 2005 and 2010) are almost the same and are both lower than observed in 1994-2004 (the end of the red line in their graph).

That this cooling would just be a temporary blip and would change nothing about global warming goes without saying and has been amply discussed elsewhere (e.g. here). But another question has been rarely discussed: will this forecast turn out to be correct?

We think not – and we are prepared to bet serious money on this. We have double-checked with the authors: they say they really mean this as a serious forecast, not just as a methodological experiment. If the authors of the paper really believe that their forecast has a greater than 50% chance of being correct, then they should accept our offer of a bet; it should be easy money for them. If they do not accept our bet, then we must question how much faith they really have in their own forecast.

The bet we propose is very simple and concerns the specific global prediction in their Nature article. If the average temperature 2000-2010 (their first forecast) really turns out to be lower or equal to the average temperature 1994-2004 (*), we will pay them € 2500. If it turns out to be warmer, they pay us € 2500. This bet will be decided by the end of 2010. We offer the same for their second forecast: If 2005-2015 (*) turns out to be colder or equal compared to 1994-2004 (*), we will pay them € 2500 – if it turns out to be warmer, they pay us the same. The basis for the temperature comparison will be the HadCRUT3 global mean surface temperature data set used by the authors in their paper.

To be fair, the bet needs an escape clause in case a big volcano erupts or a big meteorite hits the Earth and causes cooling below the 1994-2004 level. In this eventuality, the forecast of Keenlyside et al. could not be verified any more, and the bet is off.

The bet would also need a neutral arbiter – we propose, for example, the director of the Hadley Centre, home of the data used by Keenlyside et al., or a committee of neutral colleagues. This neutral arbiter would also decide whether a volcano or meteorite impact event is large enough as to make the bet obsolete.

We will discuss the scientific reasons for our assessment here another time – first we want to hear from Keenlyside et al. whether they accept our bet. Our friendly challenge is out – we hope they will accept it in good sportsmanship.

(*) We adopt here the definition of the 10-year intervals as in their paper, which is from 1 November of the first year to 31 October of the last year. I.e.: 2000-2010 means 1 November 2000 until 31 October 2010.

They’d be suckers to take your bet, especially the first part. The Nov.1994 – Oct.2004 average for HadCRUT3v is 0.3594, the average from Nov.2000 to the present is 0.4246. This means that for them to win the 2000-2010 part, the average temperature from now to Oct.2010 would have to drop to 0.1722. ‘Tain’t likely.

[Response: Congratulations, it took you just 15 minutes to work this out. Of course they know those data too, and they still went into Nature and to the media with this forecast. They must have good reasons. If they do, they will take our bet. -stefan]

I am not a scientist nor a sceptic. But i have often wondered if there was a variation or reversal of trend, by what mechanism would the heat escape? Does not the theory of GW envision a steady temerature rise? Or do variations represent data errors that mask the median trend?

[Response: There are many mechanisms for natural short-term cooling. Some are of course external– large volcanic eruptions block incoming solar radiation from reaching and being absorved by Earth’s surface. But some are internal. ENSO events, for example, can warm or cool ocean surface temperatures through exchange of heat between the surface and the reservoir stored beneath the oceanic mixed layer, and by changing the distribution and extent of cloud cover (which influences the radiative balance in the lower atmosphere). -mike]

It is interesting that if the authors are right, than global warming should go up (in fairly large) steps, rather than linearly, since the paper does not have implications for climate sensitivity. Still, given that the last decade has not seen a significant amount of warming (although any trend is swamped by noise), 20 years of little warming would give skeptics a little wiggle room. Some others such as Gavin and Tamino (and myself) have said that if there is no warming by 2015 (perhaps 2020) then there may be something quite wrong in our understanding. Personally, I’d bet on the RC side being right here.

I respect this site a lot, but this kind of gaming seems a bit silly without a formal explanation about why you think the model is weak.

[Response: I missed the part where we implied their model is weak. We do have some issues with the experimental design and interpretation, and as we indicated in the post we will discuss those in due course. -mike]

Anyway, I suggest using the Long Bets website, it provides a good neutral clearinghouse for such things. They will also do the third-party verification and contact the necessary experts (for instance, in the event that a specific one chosen passes away prior to the completion of the bet).

I think these guys have been watching too many TH r-e-k-o-p tournaments on TV. They believe they have a good read on Mother Nature, are holding the abs nuts and have decide to go all-in. Good luck guys!

Isnt this paper all a bit of a storm in a teacup? From their graph that you show, if you run a line through the 1995 values and the 2025 values the slope is still steeper than the pre 1995 values.

If they have identified a sink (increased fragmentation and hence increased surface area of ice sheets, mayhap?) that initiated stronger dT uptake C1995 and which will be saturated (gulp – ?melted?) C2010 when their green line kicks up to a much faster dT per year than A1B then so what? Well found – what is the sink? More understanding is good.

But by 2025 they arrive at the same answer as A1B but go through 2025 at a much higher rate of dT per year. Please ask them about that!

OK, I’m a layperson, albeit one with an intense interest in the subject at hand. So please don’t throw too many rocks when I ask:

When we’re talking about “warming”, what exactly is warming? The air? The oceans? Ice that’s no longer part of glaciers or Arctic sea ice but is now water? (The graph reproduced above is labeled “global mean surface temperature”, which sounds to my untrained ear like air temperatures.)

My point is that I could easily see how the entire system in question could be warming, but because of transient effects, like weather patterns, the additional heat energy could easily wind up not where we’re measuring it for months or even years at a time. (I’ve been particularly interested in the Arctic sea ice situation the last few years. How many calories does it take to melt such vast amounts of ice? And how much apparent cooling could that cause if we’re measuring just air temps?)

I’m far less concerned with where the heat energy is in the short run than the fact that the overall amount continues to increase.

Right, this should be not be be about betting on horses. This is all about serious science. These scientists are not denialists, they just postpone climate change in some regions for approx. 10 years. This is not a forum for betting on horses, it is a science forum”

What is your level of confidence in the prediction made by GISS: “barring the unlikely event of a large volcanic eruption, a record global temperature clearly exceeding that of 2005 can be expected within the next 2-3 years.”

Does this prediction and the confidence with which it is made “The quasi-regularity of some natural climate forcing mechanisms, combined with knowledge of human-made forcings, allows projection of near-term global temperature trends with reasonably high confidence”, reflect the consensus of climate scientists, in your opinion?

Yes, the paper is a storm in the teacup but over here in Germany it was was not fully understood, because it does not question the basic theory of cliamte change. I think it is just another model. But their theory cannot be easily dismissed. It is a quality piece of paper (good points, bad points), but I think realclimate was a little premature to answer it. However, the theory of cliamte change remains consistent.

“Climate Change, Sea Level, and Western Drought: Dangerous Anthropogenic Interference
Learn why the American West could be in trouble with surface air temperatures rising faster than elsewhere in the coterminous United States. Dr. Jonathan Overpeck, director of the Institute for the Study of Planet Earth at the University of Arizona, and recipient of the shared 2007 Nobel Peace Prize for his role as a Coordinating Lead Author for the UN Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment, will address the trend of droughts in the west and the vulnerability of coastal communities as they face sea level rise coupled with increasing storm intensities. This program is presented by JISAO, which fosters research collaboration between the University of Washington and the National Oceanographic and Atmospheric Administration.”

Isn’t it odd that their so-called “verification” period indicates no global warming between 1985-1998? Since that is hugely incorrect, are we to conclude that their model is not very predictive? Or does “verification” mean something else in this context?

Shame on RealClimate for turning a serious scientific subject into a bet. If these authors are wrong please use the scientific method – evidence, reasoning, and yes climate models (if predictions vary) to convince others.

“To be fair, the bet needs an escape clause in case a big volcano erupts”

There is currently a big volcano erupting.

[Response: In full: “…the bet needs an escape clause in case a big volcano erupts or a big meteorite hits the Earth and causes cooling below the 1994-2004 level.” You forgot the last part. Whether this volcano will do that remains to be seen. Btw. – did Pinatubo leave even a blip in the red curve above? Remember we are talking 10-year averages. -stefan]

Re #12: It’s air temperature that is being discussed. Melting large quantities of ice requires large amounts of energy, and this slows the rate at which temperature would rise with the same energy input but no melting, but it is not a major effect. Also higher rates of ocean water evaporation produce a similar effect. In combination these two could possibly produce a “measurable” decline in the rates of warming, but I suspect that it would be measurable only if there was an equivalent Earth without the greater melting and evaporation rates so that a comparison could be made.

There really should be more emphasis on the overall effects of energy added to the troposphere and the upper oceans. Average air temperature is an important indication of energy changes, but it doesn’t tell us everything.

E.g., Assuming that the Keenlyside paper turns out to be accurate, it would mean that energy would be transferred from the atmosphere to the oceans at a higher rate for a time and then a lower rate. For the first period we might seem to be better off, but there are significant negative effects with a warmer ocean system. One of them seems to be a reduction in dissolved oxygen. If this passes tipping points in large enough volumes, there could be additional collapses in marine life beyond what we directly produce with overfishing and pollution.

I’m not at all sure that the net effect would be positive during the predicted 10 year period.

The point is that as long as greenhouse gases are reducing the rate of radiation from the land oceans and lower atmosphere, there may be no distribution of the net energy increase that results in good news. Those who might think that a ten year pause in air temperature increases gives us extra time are not looking at the whole picture.

Lou Grinzo (12) — I am under the impression that HadCRUTv3 uses air temperatures on land and sea surface temperatures in the oceans to produce their global mean.

Ayelén (19) & C. W. Magee (20) — Impressive as it may appear, Caiten is not that much of a volcano nor produces that big an eruption. There is probably a volcano site which will give you an estimate of the current eruption’s VEI. I believe it will be on the smaller end of the scale.

//”What about the eruption of Chaiten vulcano in Chile, is it suficiently important to affect the climate?”//

Not likely. Volcanic eruptions don’t necessarily need to cause significant cooling. You need to look at the sulfuric-acid particles (aerosols). The eruption of El Chichon for example was significantly less explosive than Mount St. Helens a couple years earlier, but the former caused a lot more cooling because it emitted far greater quantities of SO2 gas, whereas Mount St. Helens was largely fine ash that settled out.

#12 Lou:

In fact the troposphere heats and cools pretty uniformily as a unit, so the surface and atmosphere will all heat up, at least until you get up very high and enter the stratosphere. Land and oceans will heat up(most of the heat goes into the oceans), though land heats quicker because it has a lower heat capacity. Though keep in mind that different regions are affected by global warming. Some might not change much at all, while others are effected a lot more. Also keep in mind (as Gavin mentions) that there is a lot of short-term “noise” that will offset warming, or even cause cooling on short timescales (such as years to a decade or longer).

Jim Cross, betting is a time honored technique for judging “degree of belief” or subjective probability. We place sufficient faith in it to determine prices for stocks and commodities. I don’t see the problem with doing a little applied Bayesian probability in climate science ;-)

“Experts are now waiting to see whether the volcano will affect the world’s climate.

“So far, Chaiten has emitted only a few thousand tons of sulphur dioxide.

“In general, a volcano must spew at least one million tons of sulphur dioxide into the stratosphere to have a global effect on climate.

“After eruptions of unusual size, sulphur dioxide, converted into sulphuric acid, can form a thin white cloud in the atmosphere that reflects sunlight away from Earth.

“The Philippines’ Mount Pinatubo produced a brief cooling of the climate after spewing 20 million tons of sulphur dioxide in 1991.”

[Response: Moreover, most of the climatically-relevant volcanic eruptions are the explosive tropical eruptions (El Chichon, Pinatubo, Agung, Tambora, Krakatoa, etc), because the general circulation of the stratosphere is such that the aerosols are transported poleward from the source latitude. So only tropical eruptions tend to blanket the global lower stratosphere, which is how you get a substantial global mean cooling. There are exceptions (e.g. the Laki eruption of 1783 in Iceland). Nonetheless, as Chaiten is located well outside the tropic, I wouldn’t expect much in the way of any global climate impact. And more specifically, I don’t see it being a deal-breaker for the bet in question. -mike]

Great idea, though I doubt Keenlyside et al. will be amused. If this were to grow into a larger betting pool I would be strongly inclined to bet with RC, in spite of the fact that this is so short term that it may be more like betting on weather than climate. Nearly every paper that I have seen recently that has indicated a meaningful change in rate for a variable related to warming has suggested that, if anything, average model sensitivity may be too low, with positive feedbacks underestimated. I agree with others that consider this a pretty bold forecast by Keenlyside et al. since I think that 2005-2007 were warmer than 1994-2004 requiring that 2008-2010 exhibit quite a steep cooling trend for their forecast to pan out.

Mike:
Given that there are generally only 0-3 VEI 6+ eruptions per century (Of which Chaiten might eventually become one, albeit at high latitude winter), why not just suck up the few % risk and drop the escape clause?

Having looked at their paper and their press release, I think the terms of your bet may be a little misplaced.

If you were living on a Keenlyside Earth and your global mean temperature followed their model, then you would still see warming, i.e. their model for 2000-2010 is warmer than their model for 1994-2004. So on the Keenlyside Earth the warming slows rather than stops.

This jives with their press release: “The improved predictions suggest that global warming will weaken slightly during the following 10 years.” Where I assume “weaken” is intended to mean “slow” rather than being a prediction of cooling. A more natural bet therefore might be to ask whether the real Earth warms faster or slower than the Keenlyside Earth.

In my opinion, it is only by willfully ignoring the misfit in their model at 1994-2004 that one would suggest that actual temperatures in 2005-2015 should be predicted to be colder than 1994-2004.

[Response: Robert, this is something we discussed with the authors before proposing the bet. The green points, despite being connected by a line, do not represent one model run. Rather, each green point is an individual forecast starting from somewhere near the red line. That is why in the paper they say they predict a slight cooling relative to 1994-2004. You are right that already their prediction (or better to call it hindcast) for the 1994-2004 period was too cold. Otherwise, if you compare the green and black curves from 1999-2010, their evolution is the same, they are simply offset. So if you just took the relative change since 1999, not the absolute numbers as compared to the red curve, their new model would predict the same warming as a standard scenario run (i.e. the black one), which would hardly have been a reason to go to the worldwide media with a “pause in warming” prediction. -stefan]

I respect this site and its group of contributors greatly, but like Jim Cross I am disappointed to see this post as I think it trivialises the issues involved. Ray Ladbury, who I also respect, suggests that there no “problem with doing a little applied Bayesian probability in climate science” in this way. That would be fine to do in private with colleagues who understand the issues intimately, but this site attracts a lot of lay-people who come here for clear explanations of climate change science and informed debate on current topics. The take-away message from this post for a lay-person is that it is a game we are playing.

How pathetic. This bet is predicated on the assumption that the authors of the paper in question are “denier” sympathizers, placing them in an antagonistic position. Clearly what is at question is the science, not the scientists` beliefs. What kind of scientists would bet on their findings to add strength to their accuracy?

The people at Real Climate are behaving very childishly on this. Just address the science and leave punditry to punters. Please. Are you trying to bring the level of discussion down to that of Fox News? Do you justify your actions by playground slogans like “he started it”?

[Response: We are absolutely not proposing this on the assumption that the authors are “denier sympathizers”. The authors are very good and respected colleagues, and this post is entirely about the ability to predict natural climate variability a decade ahead. It is not about anthropogenic warming, a topic on which we completely agree with Keenlyside et al. The short time scale of this prediction makes it amenable to have some fun with a bet, because the outcome will be seen in a reasonable time frame. If for some a bet is not “serious” enough, we will follow it with a serious discussion of the scientific issues shortly. We think framing this as a bet with specified conditions will help to clarify what exactly it is that the authors are predicting – after reading the paper at first this was not entirely clear to us, and it clearly is not entirely clear to many of the journalists reporting on it either. -stefan]

I must have missed a link to the full article along the way. I only see links to the abstract.

The article is copyright of Nature, and it would be unethical to provide free access to an article which the copyright owners don’t approve. If you want to purchase access, you can do so through the Nature website.

This is very sad that RC has been reduced to a carnival like betting on global warming.

What’s sad is that the denialosphere has made such a mockery of the Keenlyside et al. publication. The authors make it clear that they don’t disagree with the reality of global warming, but blogs everywhere are using it as a propaganda tool to paint global warming as a fraud and the climate science community as a bunch of confused clowns. I’d say that this RC article is an effective countermeasure in the propaganda war.

I don’t think bets prove anything, but if this proposal gets the point across then to the RC guys I say: good on ya. And as I said before, the data already available make it nearly impossible for Keenlyside et al.’s prediction for the 2000-2010 average to be supported by the data.

regards #19: I read this week (probably in sciencedaily) that the geological evidence of the last Chaiten eruption shows a lot of ash, but not much SO2. If this bears out, even if the current eruption ended up being large (that is probably already only a small probability) the sulfates would still likely not be enough.

I’m not so sure about the effects of eruption latitude. My (nonexpert) recollection is the high latitude eruptions would mean most of the aerosols would end up in the hemisphere of the eruption. I would think that the overall effect on global average would be similar, but concentrated on one hemisphere only.

You need greater confidence than 50% to be motivated to make a bet. In some cases, much greater than 50%. Why? Because volatility destroys value (Sharpe Ratio). Depending on my utility curve and the size of the bet, I might need to be 99% sure or more before entering into the bet.

This is such a simple and common lesson in statistics that I find it hard to trust a statistical scientist who doesn’t understand it. In particular, I find it hard to believe that somebody would be employed in complex modeling tasks without immediate recognition of the application.

Perhaps I’m just out of touch with the times, but I agree completely with Chris McGrath in #33. This post would be crass even as an addendum to a serious discussion of the paper, but as a substitute for such a discussion (to be supplied at some future date) it’s an embarrassment. I don’t see why Tamino considers scientists engaging in a propaganda war a good thing – I haven’t seen him doing it.

as a follow up to your comment on volcanic aerosol transport, I was curious as to how fast anthropogenic aerosols are spread before they are removed, and if they are totally confined to the troposphere? They tend to have a reputation for being regional, but during the mid-century slight cooling, the Northern Hemisphere as a whole seemed to be effected.

I disagree – there is nothing frivolous in this post. Besides, scientists aren’t dead serious all the time – they like to have fun. That’s why a lot of science gets discussed over beers at the pub during scientific conferences. If you are surprised by this, read James Watson’s “The Double Helix,” about the discovery of DNA structure. Or Horace Judson’s “The Eighth Day of Creation,” which gives an inside look at the scientists (including Watson and Crick) responsible for the revolution in molecular biology during the mid-20th century.

I find this post to be at best foolish and at worst reprehensible. To make the claim that if someone doesn’t accept your silly bet that they must not believe in their published article is childish. I would expect the same behavior from 10 year old boys on the playground. I am sure that the multiple authors of this article thought that this would be a good idea in the heat of the moment but I hope that they have the maturity to realize that it was poor judgment after a few nights sleep and pull this ludicrous article.

Is the new standard that all scientific articles should be judged by in the future? The scientist must not only put his reputation on the line by publishing the article for all to review and discuss but also must be willing to accept all monetary bets that dissenters throw out? To think that this site actually condemned others for paid speaking engagements in NYC a few weeks back. Where is the “discussing ideas and data in order to advance scientific understanding” (your words from your Jan 30 post).

What happened to the common courtesy of yesteryear when if there was a disagreement between gentlemen they shook hands and engaged in a “gentleman’s bet”. Even the crooks in “Trading Places” only bet one dollar when they ruined two peoples lives. Perhaps we should go back to the time of Hamilton and Burr and you guys can fight for your honor with dueling pistols.

I have typically publicly praised your site for its scientific knowledge. Now I have no choice but to write a rather viscious critique on my site that tries to discuss global warming with civility. At one time I thought this site was populated by scientists that were trying to explain complicated science. I guess I was wrong, it is run by children that want to show that they can beat up on others.

If you have a bone to pick with AR over his having ——-ed (supply your own descriptive verb) his reporting of the Keenlyside et al. paper, could you please send him an e-mail instead of blasting him in the NYT blog? It might be a more productive way of imparting better information. Thank you.

None of the forecasts appear quite right, they are too conservative, specially for the 2005-2010 period. Almost known to be quite warm. Gisstemp .76. .65 and .73 C for 2005-06-07. Higher than most previous years except 1998. Before someone is going to say something like Hadley is different than GISStemp etc, My work agrees indirectly with GISStemp, and above all other reasons, a Density Weighted Temperature of the entire atmosphere would make such surface temperature graphs or projections eventually obsolete.

It is sad to me that a wager was made about our future climate. It may be somewhat in jest, but it now gives fuel to those who believe climate change (Global Warming has become a vilified word) is not real or just a money making scheme. I find that this could damage trying to get the message to ordinary citizens as it seems many on this planet are lemmings following the tune of the news media outlets and their agendas.

I am not a scientist nor am I anyone of great interest in the world but I actually do my own homework on this subject and find Climate change is real. Please Please retract this bet before it causes more damage to a science that becomes more politicized each day. The future of this planet should be more important than any ego here or of any scientist for or against this subject. Please think before you act in the future!